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This article mainly introduces the relevant knowledge of "what are the knowledge points of Android development". The editor shows you the operation process through actual cases, the operation method is simple and fast, and it is practical. I hope that this article "what are the knowledge points of Android development" can help you solve the problem.

1.1 what is Android

Android is an open source, Linux-based operating system for mobile devices such as smartphones and tablets. Android was developed by the Open Mobile Alliance, led by Google and other companies.

Android provides a unified approach to application development, which means that developers only need to develop for Android so that their applications can run on different Android-enabled mobile devices.

Google released its first beta version of Android Software Development Kit (SDK) in 2007 and the first commercial version of Android 1.0 in September 2008.

On June 27, 2012, Google announced the release of Android version 4.1 Jelly Bean at the Google Iamp O conference. Jelly Bean is a progressive update in terms of functionality and performance, mainly aimed at improving the user interface, and the Android source code is under free and open source software licenses. Most of the code released by Google follows version 2.0 of the Apache license, and the changes to the Linux kernel follow version 2 of the GNU General Public license.

The origin of 1.2Android

● in October 2003, Rubin founded Android Technology and created the Android mobile operating system. He is also known as "the father of Android".

●, Aug. 17, 2005, Google acquired Android Technologies

● established the Open Mobile Alliance under the leadership of Google on November 5, 2007

● in October 2008, the first android smartphone T-Mobile G1 released nexus. In February 2010, Linux kernel launcher Greg Kroah-Hartman removed the Android driver from the Linux kernel state tree ("staging tree"). From then on, the mainstream of Android and Linux development will go their separate ways.

● in the first quarter of 2011, Android's global market share surpassed Symbian for the first time, ranking first in the world.

In the fourth quarter of ● 2013, the global market share of Android flat phones has reached 78.1%.

Advantages of 1.3Android development

① open source ② numerous developers and powerful community ③ growing market ④ internationalized App integration ⑤ low development cost ⑥ higher chances of success ⑦ rich development environment

1.4Android library

This category includes Java-based libraries developed specifically for Android. Examples of this category library include application framework libraries, such as user interface construction, graphics, and database access. Some of the core Android libraries available to Android developers are summarized as follows:

① android.app-provides access to the application model and is the cornerstone of all Android applications.

② android.content-facilitates content access, publishing, and message delivery between applications and between application components.

③ android.database-used to access data published by content providers, including SQLite database management classes.

④ android.opengl-Java interface for OpenGL ES 3D picture rendering API.

⑤ android.os-provides applications with the ability to access tagged operating system services, including messages, system services, and interprocess communication.

⑥ android.text-renders and manipulates text on the device display.

⑦ android.view-the basic building block of the application user interface.

⑧ android.widget-A rich collection of preset user interface components, including buttons, tags, lists, layout management, radio buttons, and more.

⑨ android.webkit-A collection of classes that allow applications to be provided with built-in Web browsing capabilities.

1.5Android application components

Application components are the basic building blocks of an Android application. These components are organized by loosely coupled application manifest files.

Here are four main components that can be used in Android applications.

① Activities

An activity identifies a single screen with a user interface. For example, a mail application can contain an activity to display a new mailing list, another activity to write a message, and another activity to read a message. When the application has more than one activity, one of them is marked to be displayed when the application starts.

An activity is a subclass of the Activity class, as follows:

Public class MainActivity extends Activity {

}

② Services

A service is a component that runs in the background and performs long-term operations. For example, a service can be a user playing music in the background while using different programs, or obtaining data through the network during an activity without blocking user interaction.

A service is a subclass of the Service class, as follows:

Public class MyService extends Service {

}

③ Broadcast Receivers

The broadcast receiver simply responds to broadcast messages from other applications or systems. For example, an application can initiate a broadcast to instruct other applications that some data has been downloaded to the device and can be used by them. Therefore, the broadcast receiver will intercept these communications and take appropriate action.

The broadcast receiver is a subclass of the BroadcastReceiver class, and each message is broadcast as an Intent object.

Public class MyReceiver extends BroadcastReceiver {

}

④ Content Providers

The content provider component provides data from one application to another by request. These requests are handled by methods of the ContentResolver class. This data can be stored in a file system, database, or other place.

The content provider is a subclass of the ContentProvider class and implements a standard set of API for other applications to perform transactions.

Public class MyContentProvider extends ContentProvider {

}

1.6Android architecture

The Android operating system is a stack of software components, which can be roughly divided into five parts and four main layers in the architecture diagram.

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